Method of processing plate-shaped workpiece

ABSTRACT

A method of processing a plate-shaped workpiece includes a workpiece supporting step of placing a plate-shaped workpiece on an upper surface of a sheet whose area is larger than that of the plate-shaped workpiece through a liquid resin interposed therebetween and supporting the plate-shaped workpiece on only the liquid resin that has solidified and the sheet, a processing step of processing the plate-shaped workpiece to divide the plate-shaped workpiece into a plurality of chips, and a pick-up step of picking up the chips from the sheet.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method of processing a plate-shapedworkpiece.

Description of the Related Art

Wafers having, on their face sides, a plurality of devices such asintegrated circuits (ICs) or large-scale integration (LSI) circuitsformed in respective areas demarcated by a plurality of projected dicinglines are divided into individual device chips by a cutting apparatus ora laser processing apparatus. The device chips will be used inelectronic appliances such as mobile phones and personal computers.

After such a wafer has been divided into individual device chips, apick-up step is carried out on the device chips that are still kepttogether in a wafer configuration similar in shape to the wafer as awhole. Heretofore, as illustrated in FIG. 7 of the accompanyingdrawings, it has been the general practice to support a wafer 10 by anadhesive tape T on an annular frame F having an opening Fa that isdefined centrally therein and that accommodates the wafer 10 therein andto deliver the wafer 10 thus supported to a cutting apparatus or a laserprocessing apparatus for processing the wafer 10 (see, for example,Japanese Patent Laid-open No. Hei 10-242083, Japanese Patent Laid-openNo. 2002-222988, and Japanese Patent Laid-open No. 2004-188475). Thewafer 10 illustrated in FIG. 7 is a circular, plate-shaped workpiecehaving devices 12 formed in respective areas demarcated on a face side10 a thereof by a grid of projected dicing lines 14. The frame F has apair of recesses Fb and Fc defined in an outer circumferential edgeportion thereof for distinguishing between face and reverse sides of theframe F and defining a direction in which the frame F supports the wafer10.

SUMMARY OF THE INVENTION

The processing apparatus disclosed in Japanese Patent Laid-open No. Hei10-242083, Japanese Patent Laid-open No. 2002-222988, and JapanesePatent Laid-open No. 2004-188475 described above repetitively uses theframe F for supporting the wafer 10. Therefore, after the wafer 10supported by the frame F has been processed, the adhesive tape T isremoved from the frame F, and thereafter the frame F is retrieved. Theretrieved frame F is serviced for maintenance, e.g., cleaned to removedebris, an adhesive, etc., deposited on the frame F and stored in agiven place until it will be used to support a wafer. However, since themaintenance process is tedious and time-consuming, the overall processfor processing wafers is low in productivity.

It is therefore an object of the present invention to provide a methodof processing a plate-shaped workpiece with higher productivity withoutthe need for a maintenance process for a frame that supports theplate-shaped workpiece.

In accordance with an aspect of the present invention, there is provideda method of processing a plate-shaped workpiece, including a workpiecesupporting step of placing the plate-shaped workpiece on an uppersurface of a sheet whose area is larger than that of the plate-shapedworkpiece through a liquid resin interposed therebetween and supportingthe plate-shaped workpiece on only the liquid resin that has solidifiedand the sheet, a processing step of processing the plate-shapedworkpiece to divide the plate-shaped workpiece into a plurality ofchips, and a pick-up step of picking up the chips from the sheet.

Preferably, the method further includes an expanding step of expandingthe sheet to widen distances between the chips. Preferably, the methodfurther includes after the pick-up step, a discarding step of discardingthe sheet.

Preferably, the processing step includes either a cutting step ofpositioning a cutting blade on a region to be divided of theplate-shaped workpiece and cutting the plate-shaped workpiece with thecutting blade, a laser ablation step of applying a laser beam having awavelength absorbable by the plate-shaped workpiece to a region to bedivided of the plate-shaped workpiece to form grooves in theplate-shaped workpiece by way of laser ablation, or a modified layerforming step of applying a laser beam having a wavelength transmittablethrough the plate-shaped workpiece to a region to be divided of theplate-shaped workpiece while positioning a focused spot of the laserbeam within the plate-shaped workpiece to form modified layers in theplate-shaped workpiece.

Preferably, the plate-shaped workpiece is a wafer including a face sidehaving a plurality of devices formed in respective areas demarcatedthereon by a plurality of projected dicing lines, the face side of thewafer or a reverse side thereof being placed on the upper surface of thesheet through the liquid resin interposed therebetween. Preferably, thesheet is made of a polyester- or polyethylene-based material.Preferably, the liquid resin is an acryl-, rubber-, silicone-, orepoxy-based liquid resin.

According to the aspect of the present invention, since the method ofprocessing a workpiece includes a workpiece supporting step of placing aplate-shaped workpiece on an upper surface of a sheet whose area islarger than that of the plate-shaped workpiece through a liquid resininterposed therebetween and supporting the plate-shaped workpiece ononly the liquid resin that has solidified and the sheet, a processingstep of processing the plate-shaped workpiece to divide the plate-shapedworkpiece into a plurality of chips, and a pick-up step of picking upthe chips from the sheet, a frame that has heretofore been used is notrequired, and no tedious and time-consuming work has to be performed formaintenance to make such a frame reusable, so that the method ofprocessing a plate-shaped workpiece is of increased productivity.

The above and other objects, features and advantages of the presentinvention and the manner of realizing them will become more apparent,and the invention itself will best be understood from a study of thefollowing description and an appended claim with reference to theattached drawings showing a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cutting apparatus for use in a methodof processing a plate-shaped workpiece according to an embodiment of thepresent invention;

FIG. 2A is a perspective view of a sheet according to the presentembodiment;

FIG. 2B is a perspective view of a sheet according to a modification;

FIG. 2C is a perspective view of a sheet according to anothermodification;

FIG. 2D is a perspective view of a sheet according to still anothermodification;

FIG. 3 is a perspective view illustrating the manner in which a liquidresin is supplied to the sheet according to an embodiment of the presentinvention in a workpiece supporting step;

FIGS. 4A, 4B, and 4C are perspective views illustrating the manner inwhich a wafer is placed on the sheet in the workpiece supporting step;

FIGS. 5A and 5B are perspective views illustrating the manner in which acutting step according to the present embodiment is performed as aprocessing step;

FIG. 6A is a cross-sectional view, partly in side elevation,illustrating the manner in which an expanding step is carried out;

FIG. 6B is a cross-sectional view, partly in side elevation,illustrating the manner in which a pick-up step is carried out; and

FIG. 7 is a perspective view illustrating the manner in which a wafer issupported on an annular frame by an adhesive tape.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention will be describedhereinbelow with reference to the accompanying drawings.

FIG. 1 illustrates a cutting apparatus 1 in its entirety in perspectivethat is suitable for use in a method of processing a plate-shapedworkpiece according to an embodiment of the present invention. Asillustrated in FIG. 1 , the cutting apparatus 1 is an apparatus forcutting a circular wafer 10 as the plate-shaped workpiece. The wafer 10is similar to the wafer 10 described above with reference to FIG. 7 ,and is a semiconductor wafer made of silicon (Si), for example, having aplurality of devices 12 (see FIG. 4A) formed in respective areasdemarcated on a face side 10 a by a plurality of projected dicing lines14.

The cutting apparatus 1 includes an apparatus housing 2. The wafer 10 isplaced on a sheet S with a liquid resin P interposed therebetween in aworkpiece supporting step to be described in detail later. The wafer 10is supported on only the liquid resin P that has solidified and thesheet S. A plurality of wafers 10 each supported on the liquid resin Pand the sheet S are stored in a cassette 3, indicated by thetwo-dot-and-dash lines, that is delivered to the apparatus housing 2.The cassette 3 is placed on a vertically movable cassette table 3 adisposed in the apparatus housing 2. One, at a time, of the wafers 10stored in the cassette 3 is taken out of the cassette 3 and deliveredonto a temporary rest table 5 on the apparatus housing 2 when aloading/unloading mechanism 4 grips the sheet S and moves in a Y-axisdirection to bring the wafer 10 on the sheet S onto the temporary resttable 5.

The wafer 10 delivered to the temporary rest table 5 is attracted undersuction by a delivery mechanism 6, which is then turned to deliver thewafer 10 to a chuck table 7 positioned in a loading/unloading area wherethe wafer 10 is to be loaded and unloaded. The wafer 10 delivered to thechuck table 7 is placed, with its reverse side 10 b (see FIG. 4A) facingdownwardly, on a suction chuck 7 a of the chuck table 7 and held undersuction thereon. Four clamps 7 b that are angularly spaced at equalintervals around an outer circumferential surface of the chuck table 7grip and secure the sheet S in position.

The cutting apparatus 1 includes an alignment unit 8 and a cutting unit9 that are disposed over an alignment area next to the loading/unloadingarea along the X-axis direction. The apparatus housing 2 houses thereinan X-axis moving mechanism, not illustrated, for moving the chuck table7 in the X-axis direction from the loading/unloading area to thealignment area next to it and also for processing-feeding the chucktable 7 in a processing area next to the alignment area, a Y-axis movingmechanism, not illustrated, for indexing-feeding a cutting blade 9 a ofthe cutting unit 9 in a Y-axis direction perpendicular to the X-axisdirection, and a Z-axis moving mechanism, not illustrated, for liftingand lowering the cutting blade 9 a and incising-feeding the cuttingblade 9 a in the processing area. When the chuck table 7 and hence thewafer 10 placed thereon are moved in the X-axis direction by the X-axismoving mechanism to the alignment area, the alignment unit 8 with acamera function captures an image of the wafer 10 to detect a region ofthe wafer 10 to be cut by the cutting unit 9. The cutting unit 9 carriesout a cutting step as follows.

The alignment unit 8 detects one of the projected dicing lines 14 as theregion to be cut. The detected projected dicing line 14 is aligned withthe X-axis direction and hence oriented in alignment with the cuttingblade 9 a in the alignment area. The chuck table 7 is then moved fromthe alignment area in the X-axis direction by the X-axis movingmechanism to position the aligned projected dicing line 14 in theprocessing area that is directly below the cutting blade 9 a of thecutting unit 9. Then, the cutting blade 9 a is rotated about its centralaxis, and lowered or incising-fed by the Z-axis moving mechanism while,at the same time, the chuck table 7 is processing-fed by the X-axismoving mechanism, thereby cutting the wafer 10 along the projecteddicing line 14 to form a straight cut groove in the wafer 10 along theprojected dicing line 14. After the straight cut groove has been formedin the wafer 10, the Z-axis moving mechanism lifts the cutting blade 9a, and the wafer 10 is indexing-fed a distance in the Y-axis directionup to an adjacent projected dicing line 14 by the Y-axis movingmechanism. Then, in the same manner as described above, the cuttingblade 9 a is incising-fed by the Z-axis moving mechanism andprocessing-fed in the X-axis direction by the X-axis moving mechanismwhile, at the same time, the chuck table 7 is processing-fed by theX-axis moving mechanism, thereby cutting the wafer 10 along theprojected dicing line 14 to form a straight cut groove in the wafer 10along the adjacent projected dicing line 14. The above process isrepeated until straight cut grooves are formed in the wafer 10 along allthe projected dicing lines 14 that extend in a predetermined direction.Thereafter, the chuck table 7 is turned 90 degrees about its centralaxis to align one of the projected dicing lines 14 that extend in adirection perpendicular to the straight cut grooves already formed inthe wafer 10 with the X-axis direction. Then, the above cutting processis carried out again on the wafer 10 until straight cut grooves areformed in the wafer 10 along all the projected dicing lines 14 thatextend in the direction perpendicular to the straight cut grooves. Inthis manner, straight cut grooves are formed in the wafer 10 along allthe projected dicing lines 14 on the wafer 10. When the above cuttingstep has been performed on the wafer 10, the wafer 10 is divided alongthe cut grooves into individual device chips. At this time, since theindividual device chips remain supported on the sheet S by thesolidified liquid resin P, the device chips are still kept together in awafer configuration similar in shape to the wafer 10 as a whole. Thedevice chips that are divided but remain in the wafer configuration willalso be referred to as the “wafer 10.” The components described above ofthe cutting apparatus 1 are controlled in operation by a control unit,not illustrated.

The wafer 10 divided into the individual device chips in the cuttingstep described above is attracted under suction by a delivery mechanism11 from the chuck table 7 that has been moved from the processing areato the loading/unloading area. Then, the wafer 10 is delivered to acleaning device 13, details of which are omitted from illustration, bythe delivery mechanism 11. The wafer 10 is then cleaned and dried by thecleaning device 13, and thereafter delivered to the temporary rest table5 by the delivery mechanism 6. The wafer 10 is then placed back into aposition in the cassette 3 by the loading/unloading mechanism 4. Thecassette 3 on the cassette table 3 a is vertically movable by thecassette table 3 a to allow the wafer 10 to be stored in a desired oneof storage positions arranged in a vertical array in the cassette 3.

The cutting apparatus 1 according to the present embodiment is of theabove structure and operates as described above. The method ofprocessing a plate-shaped workpiece according to the present embodimentis carried out as follows.

For performing the method of processing a plate-shaped workpieceaccording to the present embodiment, either one of a first sheet S1 (seeFIG. 2A) whose area is larger than that of the wafer 10, i.e., the faceside 10 a or the reverse side 10 b thereof, and second through fourthsheets S2, S3, and S4 (see FIGS. 2B, 2C, and 2D) according tomodifications thereof is prepared as the sheet S referred to above. Eachof the first through fourth sheets S1, S2, S3, and S4 should preferablybe in the form of a sheet of thermoplastic resin, such as a polyester-or polyethylene-based material, for example. More specifically, each ofthe first through fourth sheets S1, S2, S3, and S4 is a sheet ofpolyethylene terephthalate (PET) having a thickness of approximately 0.1mm, for example.

The first sheet S1 illustrated in FIG. 2A is a regular octagonal sheet,and the second sheet S2 illustrated in FIG. 2B is a square sheet. Thethird sheet S3 illustrated in FIG. 2C is a circular sheet, and thefourth sheet S4 illustrated in FIG. 2D is a sheet similar in shape tothe contour of the frame F illustrated in FIG. 7 that has heretoforebeen in use. The fourth sheet S4 has recesses S4 b and S4 c similar inshape to the recesses Fb and Fc defined in the frame F illustrated inFIG. 7 . Though the first through third sheets S1, S2, and S3illustrated in FIGS. 2A through 2C are free of such recesses, they mayhave similar recesses. The sheet used in the method according to thepresent invention is not limited to the first through fourth sheets S1,S2, S3, and S4 illustrated in FIGS. 2A through 2D, may have an arealarger than that of the wafer 10, and may be of any shape as long as itcan be held on the chuck table 7 referred to above. In the descriptionthat follows, the first sheet S1 illustrated in FIG. 2A will bedescribed and illustrated as the sheet S according to the presentembodiment for supporting the wafer 10 as illustrated in FIG. 7 whilethe wafer 10 is being processed.

After the wafer 10 and the first sheet S1 have been prepared, in orderto place the wafer 10 on a face side Sla of the first sheet S1, a liquidresin supply unit, i.e., a liquid resin supply nozzle, 20 is positionedabove the center of the face side Sla of the first sheet S1, and drops apredetermined amount of liquid resin P onto the face side Sla of thefirst sheet S1, as illustrated in FIG. 3 . The liquid resin P is aliquid resin that solidifies over time, and may be selected from acryl-,rubber-, silicone-, and epoxy-based liquid resins, for example. Theamount of liquid resin P supplied from the liquid resin supply unit 20is large enough to spread nearly entirely over the face side Sla of thefirst sheet S1, but stay on the face side Sla of the first sheet S1, asillustrated in FIG. 4A.

After the liquid resin P has been supplied to the face side Sla of thefirst sheet S1 but before the supplied liquid resin P solidifies, thewafer 10 with its face side 10 a facing upwardly and its reverse side 10b facing downwardly is placed on the liquid resin P dropped onto theface side Sla of the first sheet S1, as illustrated in FIG. 4B.Thereafter, as a predetermined period of time elapses, the liquid resinP on the first sheet S1 solidifies, so that the wafer 10 is supported ononly the liquid resin P that has solidified and the sheet S (workpiecesupporting step). The wafer 10, the solidified liquid resin P, and thesheet S thus combined together jointly make up an integral assemblyhaving a predetermined degree of rigidity. The predetermined degree ofrigidity of the integral assembly is such that the first sheet S1 willbe kept flat when the first sheet S1 is supported at two diametricallyopposite points on its outer circumferential edge portion. According tothe illustrated embodiment, the wafer 10 is placed on the first sheet S1with the reverse side 10 b of the wafer 10 facing the face side Sla ofthe first sheet S1. However, the present invention is not limited tosuch a wafer orientation. As illustrated in FIG. 4C, the wafer 10 may beplaced on the first sheet S1 with the face side 10 a of the wafer 10facing the face side Sla of the first sheet S1.

A plurality of wafers 10 supported on respective first sheets S1 throughrespective solidified liquid resins P interposed therebetween in theworkpiece supporting step described above are stored in the cassette 3illustrated in FIG. 1 , and introduced into the cutting apparatus 1.

For carrying out the above cutting step as a processing step accordingto the present invention, one of the wafers 10 introduced into thecutting apparatus 1 is taken out of the cassette 3 by theloading/unloading mechanism 4 and temporarily placed on the temporaryrest table 5. Then, the wafer 10 is delivered by the delivery mechanism6 to the suction chuck 7 a of the chuck table 7 positioned in theloading/unloading area illustrated in FIG. 1 , and held under suction onthe suction chuck 7 a. The clamps 7 b grip and secure the outercircumferential edge portion of the first sheet S1. The wafer 10 held onthe chuck table 7 is moved by the X-axis moving mechanism from theloading/unloading area to the alignment area directly below thealignment unit 8. The alignment unit 8 detects one of the projecteddicing lines 14 as the region to be cut, and aligns the detectedprojected dicing line 14 with the X-axis direction and also with thecutting blade 9 a. Then, as illustrated in FIG. 5A, the wafer 10 ismoved in the X-axis direction by the X-axis moving mechanism to theprocessing area where the wafer 10 is positioned directly below thecutting unit 9 by the X-axis moving mechanism.

As illustrated in FIG. 5A, the cutting unit 9 includes a rotationalshaft, or a spindle, 9 b that extends in the Y-axis direction and thatis rotatably supported for rotation about its central axis parallel tothe Y-axis direction and an annular cutting blade 9 a mounted on adistal end of the rotational shaft 9 b. The cutting blade 9 a is movableby the Y-axis moving mechanism, not illustrated, so as to beindexing-fed in the Y-axis direction, as described above. The rotationalshaft 9 b is rotatable about its central axis by a spindle motor, notillustrated.

After the wafer 10 has been positioned directly below the cutting unit9, the cutting blade 9 a that is being rotated at a high speed in thedirection indicated by an arrow R1 is positioned on the projected dicingline 14 aligned with the X-axis direction. The cutting blade 9 a is thenlowered or incising-fed by the Z-axis moving mechanism to cut into thewafer 10 from the face side 10 a thereof while the chuck table 7 isbeing processing-fed in the X-axis direction, thereby forming a cutgroove 100 as illustrated in FIG. 5A. The cutting step is repeated untilcut grooves 100 are formed in the wafer 10 along all the projecteddicing lines 14 established on the wafer 10, as illustrated in FIG. 5B.The wafer 10 is now divided along the cut grooves 100 into individualdevice chips 12′.

Even after the wafer 10 has been divided into the individual devicechips 12′ in the cutting step, the device chips 12′ are still kepttogether in a wafer configuration similar in shape to the wafer 10 as awhole because the device chips 12′ are supported on the first sheet S1through the solidified liquid resin P interposed therebetween.

After the cutting step has been carried out as described above, anexpanding step and a pick-up step are carried out to pick up the devicechips 12′ from the first sheet S1 as described below. The expanding stepand the pick-up step are carried out using a pick-up apparatus 40illustrated in FIGS. 6A and 6B. The pick-up apparatus 40 includes anexpanding mechanism 42 for carrying out the expanding step of expandingthe first sheet S1 in its plane to expand the distances between adjacentones of the device chips 12′.

As illustrated in FIGS. 6A and 6B, the expanding mechanism 42 includes ahollow cylindrical expansion drum 42 a, a plurality of upwardlyextending air cylinders 42 b disposed adjacent to and around theexpansion drum 42 a and angularly spaced circumferentially around theexpansion drum 42 a, an annular holder 42 c joined to each of upper endsof piston rods of the air cylinders 42 b, and a plurality of clamps 42 dmounted on an outer circumferential surface of the holder 42 c andangularly spaced circumferentially around the holder 42 c. In FIGS. 6Aand 6B, some components are illustrated in cross section forillustrative purposes. According to the present embodiment, theexpansion drum 42 a has an inside diameter equal to or larger than thediameter of the wafer 10, and has an outside diameter smaller than thediameter of the first sheet S1. The holder 42 c has an outside diametercommensurate with the diameter of the first sheet S1, so that the firstsheet S1 is placed on the holder 42 c, and the first sheet S1 has anouter circumferential edge portion placed on a flat upper surface of theholder 42 c.

As illustrated in FIGS. 6A and 6B, the air cylinders 42 b lift and lowerthe holder 42 c between a reference position where the upper surface ofthe holder 42 c lies substantially at the same height as the upper endof the expansion drum 42 a indicated by the solid lines and an expandingposition where the upper surface of the holder 42 c is lower than theupper end of the expansion drum 42 a indicated by the two-dot-and-dashlines. In FIGS. 6A and 6B, the expansion drum 42 a is illustrated asbeing lifted and lowered with respect to the holder 42 c forillustrative purposes. In practice, however, the holder 42 c is liftedand lowered with respect to the expansion drum 42 a.

As illustrated in FIG. 6B, the pick-up apparatus 40 further includes apick-up unit 44 in addition to the expanding mechanism 42. The pick-upunit 44 includes a pick-up collet 44 a for sucking one device chip 12′at a time and a pusher mechanism 44 b that is disposed in the expansiondrum 42 a and that pushes a device chip 12′ upwardly. The pushermechanism 44 b is movable horizontally in the directions indicated by anarrow R4, and includes a push rod 44 c that can be protruded andretracted in the vertical directions indicated by an arrow R5.

As illustrated in FIG. 6B, the pick-up collet 44 a is movablehorizontally and vertically. The pick-up collet 44 a is fluidlyconnected to a suction source, not illustrated, that draws air in thedirection indicated by an arrow R7, thereby creating a negative pressurein a suction nose 44 d mounted on a distal end of the pick-up collet 44a to attract a device chip 12′ under suction on a lower end surface ofthe suction nose 44 d.

In the expanding step, as illustrated in FIG. 6A, the outercircumferential edge portion of the first sheet S1 with the wafer 10 asdivided into the device chips 12′ facing upwardly is placed on the uppersurface of the holder 42 c that is disposed in the reference position.Then, the clamps 42 d are actuated to secure the outer circumferentialedge portion of the first sheet S1 to the upper surface of the holder 42c. Then, the holder 42 c is lowered in the direction indicated by anarrow R2 toward the expanding position, exerting tensile forces on acentral area Slc of the first sheet S1 in radially outward directionsindicated by an arrow R3. At this time, a heating unit, not illustrated,disposed near the first sheet S1 should preferably have been energizedto heat the first sheet S1. In a case where the first sheet S1 is madeof thermoplastic resin as described above, the first sheet S1 can besoftened when the heating unit heats the first sheet S1 to a temperatureclose to the fusing point of the material thereof. As indicated by thetwo-dot-and-dash lines in FIG. 6A, an area of the first sheet S1 thatsupports the wafer 10 thereon is expanded in its plane, widening thedistances between the device chips 12′. In a case where the cut grooves100 formed in the wafer 10 along the projected dicing lines 14 in thecutting step are wide enough, the expanding step may be omitted.

After the expanding step has been carried out as described above, asillustrated in FIG. 6B, the suction nose 44 d of the pick-up collet 44 ais positioned above one of the device chips 12′ that is to be picked up,and the pusher mechanism 44 b is moved horizontally in a directionindicated by the arrow R4, to a position below the device chip 12′ to bepicked up. Then, the push rod 44 c of the pusher mechanism 44 b isextended in an upward direction indicated by the arrow R5, pushing upthe device chip 12′ from below. Concurrently, the pick-up collet 44 a islowered in a direction indicated by an arrow R6, and attracts the devicechip 12′ under suction on the lower end surface thereof. Then, thepick-up collet 44 a is lifted to peel the device chip 12′ off from thefirst sheet S1, thereby picking up the device chip 12′. Then, the devicechip 12′ that has been picked up is delivered to a container, notillustrated, such as a tray, or to a predetermined position for a nextstep. The above pick-up process is carried out successively on all thedevice chips 12′ on the first sheet S1 (pick-up step).

After the pick-up step has been carried out as described above, thefirst sheet S1 is discarded into a dustbin and disposed of (discardingstep). The first sheet S1 is much less costly than the frame F (see FIG.7 ) that has heretofore been used, only the first sheet S1 and theliquid resin P are required, and the first sheet S1 and the liquid resinP are rigid enough to hold the wafer 10 thereon. Therefore, the frame Fis not required, and no tedious and time-consuming work has to beperformed for maintenance to make the frame F reusable, so that themethod of processing a plate-shaped workpiece is of increasedproductivity.

The present invention is not limited to the embodiment described above.According to the above embodiment, the processing step of processing thewafer 10 to divide the wafer 10 into a plurality of device chips 12′ isthe cutting step of positioning the cutting blade 9 a in alignment withthe projected dicing lines 14 on the wafer 10 and cutting the wafer 10with the cutting blade 9 a along the projected dicing lines 14 to formthe cut grooves 100 in the wafer 10 along the projected dicing lines 14.However, the processing step may instead be a laser ablation step ofapplying a laser beam having a wavelength absorbable by the wafer 10 toa region to be divided of the wafer 10 along the projected dicing lines14 to form grooves in the wafer 10 along the projected dicing lines 14by way of laser ablation. Alternatively, the cutting step describedabove may be replaced with a modified layer forming step of applying alaser beam having a wavelength transmittable through the wafer 10, to aregion to be divided of the wafer 10 while positioning a focused spot ofthe laser beam within the wafer 10 to form modified layers in the wafer10 along the projected dicing lines 14. In a case where the grooves areformed in the wafer 10 along the projected dicing lines 14 in the laserablation step or the modified layers are formed in the wafer 10 alongthe projected dicing lines 14 in the modified layer forming step, thewafer 10 can more reliably be divided into individual device chips 12′by external forces imposed thereon in the expanding step.

The present invention is not limited to the details of the abovedescribed preferred embodiment. The scope of the invention is defined bythe appended claim and all changes and modifications as fall within theequivalence of the scope of the claim are therefore to be embraced bythe invention.

What is claimed is:
 1. A method of processing a plate-shaped workpiece,comprising: a workpiece supporting step of placing the plate-shapedworkpiece on an upper surface of a sheet whose area is larger than thatof the plate-shaped workpiece through a liquid resin interposedtherebetween and supporting the plate-shaped workpiece on only theliquid resin that has solidified and the sheet; a processing step ofprocessing the plate-shaped workpiece to divide the plate-shapedworkpiece into a plurality of chips; and a pick-up step of picking upthe chips from the sheet.
 2. The method of processing a plate-shapedworkpiece according to claim 1, further comprising: an expanding step ofexpanding the sheet to widen distances between the chips.
 3. The methodof processing a plate-shaped workpiece according to claim 1, furthercomprising: after the pick-up step, a discarding step of discarding thesheet.
 4. The method of processing a plate-shaped workpiece according toclaim 1, wherein the processing step includes a cutting step ofpositioning a cutting blade on a region to be divided of theplate-shaped workpiece and cutting the plate-shaped workpiece with thecutting blade.
 5. The method of processing a plate-shaped workpieceaccording to claim 1, wherein the processing step includes a laserablation step of applying a laser beam having a wavelength absorbable bythe plate-shaped workpiece to a region to be divided of the plate-shapedworkpiece to form grooves in the plate-shaped workpiece by way of laserablation.
 6. The method of processing a plate-shaped workpiece accordingto claim 1, wherein the processing step includes a modified layerforming step of applying a laser beam having a wavelength transmittablethrough the plate-shaped workpiece to a region to be divided of theplate-shaped workpiece while positioning a focused spot of the laserbeam within the plate-shaped workpiece, to form modified layers in theplate-shaped workpiece.
 7. The method of processing a plate-shapedworkpiece according to claim 1, wherein the plate-shaped workpiece is awafer including a face side having a plurality of devices formed inrespective areas demarcated thereon by a plurality of projected dicinglines, the face side of the wafer or a reverse side thereof being placedon the upper surface of the sheet through the liquid resin interposedtherebetween.
 8. The method of processing a plate-shaped workpieceaccording to claim 1, wherein the sheet is made of a polyester- orpolyethylene-based material.
 9. The method of processing a plate-shapedworkpiece according to claim 1, wherein the liquid resin is an acryl-,rubber-, silicone-, or epoxy-based liquid resin.